Electrochemical and photoelectrochemical characterization of photoanodes based on titania nanotubes modified by a BiVO4 thin film and gold nanoparticles

Titania nanotubes (TNT) modified with thin films of bismuth vanadate (BiVO4) and gold nanoparticles (GNP) were photoelectrochemically characterized as photoanodes for water photooxidation. Presence of bismuth vanadate enhanced efficiency of photocurrent generation in comparison with pristine TNTs under visible light illumination. Besides an extended range of absorbed light, the presence of both BiVO4 and GNP reduced the charge transfer resistance as confirmed by using electrochemical impedance spectroscopy. A possible mechanism of photoexcited charge-carrier transfer based on the locations of valence and conduction bands of TiO2 and BiVO4 has been proposed. The photocurrent of the most active photoanode (Ti/TiO2/Au/BiVO4/Au) reached a stable value of about 123 μA cm−2 and was nearly 3.5 times higher than registered for pure TiO2 and c.a. 8 times higher than recorded for BiVO4.